I have a 1979 w123 with a leaking automatic climate control (ACC)unit. A few years ago I replaced the original one with a rebuilt and now it is leaking. I don't want to spend the money on another one...the car isn't worth it.

I am planning to replace the ACC with a 3/4 ball valve or gate valve set up, bypassing the ACC altogether. I only need one setting for winter (open) and one for summer (closed). Does anyone know if the ACC unit can be subsituted for 1 valve, or are 2 necessary? Is it OK to just turn off the coolant flow to the heater core, or is it necessary to circulate the engine coolant back to the engine when the heater core is valved off?

Any ideas?

Are you refering to the electrically operated valve attatched to the engine side of the fire wall? If so that should be the "Mono-Valve", from where is the leak actually coming from on it? You can perhaps replace the plunger valve inside (a common failure/repair) for about $30 and 10 minutes.

BBOB< I don't believe the '79 300 w123 has a monovalve.

Propably referring to the climate control servo.

123 driver, mail it back to chrysler who ade it in the first place!

Fix it soon because it may indicate a siezure inside and may cause over heating, my 2 cents anyhow.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

unkl300d, Yes I was referring to the climate control servo. Mine doesn't have the mono valve.

I could mail that chrysler (Imperial I think) part back to chrysler. But their people might get the bright idea to reintroduce this part to some of their new models, which would NOT be a good idea. I better let this part fade into obscurity where it belongs.

I will repost to this thread when I get around to replacing the servo unit with a ball valve. But right now it's much too cold to think about that.

This must be a common operation. I had an independant mechanic in Knoxville recommend this, which I did. Works great. You can regulate your heat via the valve by patially closing, as the weather warms. My cost of the valve, a length of copper tube and hose clamps was about $4.00, sure beats $800 for a new servo.

Do not remove or unplug the servo, as it also serves some purpose in the A/C unit, or so I am told.

I too have this crappy servo unit that was already replaced once on my '81 380SL. The heater will not work reliably if at all, although the A/C works very well. I would really like to know about this ball-valve fix and how to do it on the SL. I live in San Diego but still it gets cold from time to time. Could I get some info on this? Thanks, -JK380

It's been a while, but I think I used 1/2" ID copper water line. The servo on my 79 300TD is a black box on the front of the passenger side near the wheel well. There are two heater lines going in the front and exiting the rear of the servo. These inlet and exit nozzles are down on the bottom of the box, so disconnect them one side at a time, and run the copper lines underneath the box. Attach the heater lines to the copper line, making sure you have sufficient insert depth to use a hose clamp and not have it blow off the copper line.

Next to the box, comming from the water pump is a third line, this you cut and insert your ball valve. I actually used a gate valve, which offers more flow control. Again using the copper tubing, make nipples for either side of the valve, insert and tighten the compresion fittings, insert the valve into your line, start it up and look for leaks. Like I said, this sure fixed my problem of intermitent/no heat. Also keep in mind that I'm no mechanic, this is your basic hillbilly fix. If some mechanical type out there knows why this is a bad idea, let us know.

Good luck.

Thank you. I'll give this a try and see how it goes. I suppose I could return the system to original (w/broken servo) if I needed to. I am concerned that the bad servo might somehow impede proper coolant flow so this might be a good idea. Will the heat still be able to be turned on and off from inside the car or will I have to go under the hood to turn it on/off?

Yes, I think that is the case, that the servo is not allowing coolant to the heater core. As long as your switch is functioning, you can control on off at the dash. Remember, don't remove the servo or disconnect the electrical connections, as it plays some roll in your A/C function. This is a pretty easy fix. Clearance under the servo is a little tight when hooking the hoses to the copper line, but no big deal.

I'm gonna try this approach. I had a mechanic who inserted a large ball bearing into the hose to block it in the summer time, which worked very well. The ball/gate valve approach sounds like the hot set-up.

JCD

I bypassed the servo coolant lines on a friends rusty 1980 300D. His servo was completely shot but all he wanted was heat/defrost. I installed a $16, cable operated heater valve (for an '80s Dodge Omni!) on the firewall, with a lawnmower control fastened under the drivers dash. The original 300D system had a default mode to operate the defroster which was still functioning so my friend was very happy.

Very Happy Motoring, Mark

__________________
DrDKW

Thanks. I know what I'm do'in this weekend. Now I might be able to drive at night with the top down. -JLK380

JLK380 & JCD, I went home over the week end and looked at the by pass I did on my 300TD, and I noticed that I was mistaken about something. In the second para where I say, "coming from the water pump is a third line, cut this and insert valve."

Thats wrong, I apologize. Leave that line as is, insert the valve into one of the lines you just by passed, the one closest to the engine. If you already cut the other line, remove the valve and splice it back togeather with a short length of tubing and two hose clamps.

As I stated, I was going from memory, which for me ain't real good. I hope this has not inconvenienced anyone.

Thanks.
Andy.

aross:

I haven't done anything yet. I looked at the servo and the hoses go in from side to side (they run thru the servo from left side of car to right side of car. So I guess that I only need to connect these lines directly and insert a valve into only ONE of them? Does it matter which one? -JLK380.

Mine ('79 Model) is different, as they run front to rear. So it is a guess as to which line to insert the valve into. It probably does not matter, since one is probably an inlet and the other an outlet. I don't see that anything could be damaged, you are just trying to start/stop flow to a heater coil.

Have fun.
Andy